The url is for the admin page I’m assuming your referring to this page.
https://boomerbalancebikes.co.uk/facebook-offer/.
Since your only wanting to do this for a single page and not the entire site you would probably want to create a template for your theme. You would want to create a child theme and add the template into it.
Here the instructions for creating a child theme. https://codex.www.ads-software.com/Child_Themes. You just need to create a folder with the name you want to call your new child theme and add 2 files. Your style.css and the functions.php file. You can copy the code from the codex and just changes the theme name and template.
style.css
<?php
/*
Theme Name: <<your theme name >>
Theme URI: https://example.com/twenty-twelve-child/
Description: Child Theme description
Author: your name
Author URI: site url
Template: twentytwelve
Version: 1.0.0
License: GNU General Public License v2 or later
License URI: https://www.gnu.org/licenses/gpl-2.0.html
Tags: light, dark, two-columns, right-sidebar, responsive-layout, accessibility-ready
Text Domain: twenty-fifteen-child
*/
?>
functions.php
<?php
add_action( 'wp_enqueue_scripts', 'theme_enqueue_styles' );
function theme_enqueue_styles() {
wp_enqueue_style( 'parent-style', get_template_directory_uri() . '/style.css' );
}
?>
To create your template You need to create a template file which is very easy.
just create a file with this header
<?php
/*
Template Name: Full Width Page
*/
if you look in the twentytwelve folder you will see a folder called page-templates open the file called full-width.php. You will want to copy everything except the comments at the top. Starting at the line that starts with get_header() and paste it into your new template under your header.
Should look something like this.
<?php
/**
* Template Name: nonav
*
*
*/
get_header('nonav'); ?>
<div id="primary" class="site-content">
<div id="content" role="main">
<?php while ( have_posts() ) : the_post(); ?>
<?php get_template_part( 'content', 'page' ); ?>
<?php comments_template( '', true ); ?>
<?php endwhile; // end of the loop. ?>
</div><!-- #content -->
</div><!-- #primary -->
<?php get_sidebar(); ?>
<?php get_footer(); ?>
Save it with the name you want to call your template you could call it for example you could call it landingpage.php.
You will next need to create a new header called header-nonav.php.
To do this open the header.php file. delete the section for the navigation
` <nav id=”site-navigation” class=”main-navigation” role=”navigation”>
<button class=”menu-toggle”><?php _e( ‘Menu’, ‘twentytwelve’ ); ?></button>
<a class=”assistive-text” href=”#content” title=”<?php esc_attr_e( ‘Skip to content’, ‘twentytwelve’ ); ?>”><?php _e( ‘Skip to content’, ‘twentytwelve’ ); ?></a>
<?php wp_nav_menu( array( ‘theme_location’ => ‘primary’, ‘menu_class’ => ‘nav-menu’ ) ); ?>
</nav><!– #site-navigation –>`
and save it as header-nonav.php and you should be done.
When you create a new page you will see a drop down called templates just select the template you created and it should work for you.
Sorry the post is so long.